- Update to version 0.21.2
* protocol
- operator "=~" matches a regular expression
- operator "contains" matches substrings
* decoder
- ffmpeg: require FFmpeg 3.1 or later
- ffmpeg: fix broken sound with certain codecs
* output
- alsa: fix high CPU usage with dmix
- httpd: fix three crash bugs
* mixer
- alsa: fix more rounding errors
* fix zlib support
- Remove mpd-zlib.patch which was already merged upstream.
- Add systemd pre(un)/post(un) macros for mpd.socket